The invention relates to a method for evaluating the donning properties of hosiery and a device which can be used to perform the method. More specifically, the invention relates to a method for simulating and measuring frictional and compressive forces that a patient would experience when donning a stocking, and an apparatus for measuring those forces.
Compression stockings are commonly used for a wide variety of medical purposes including the prevention of the formation of embolisms in the legs of bed-ridden or sedentary people, to enhance circulation, and to assist in controlling swelling. Stockings for the legs are generally circularly knit and designed to provide a certain degree of compression to an underlying limb when worn. In many cases, the compression is graduated along the length of the stocking such that the stocking not only conforms to the contours of a wearer""s leg, but the pressure in different sections of the stocking is varied according to where more or less compression is desired for the particular wearer. For example, one type of compression stocking divides the leg of a wearer into elements A through E where A corresponds to the foot, B corresponds to the ankle, C corresponds to the calf, D corresponds to the region below the knee and E corresponds to the knee, and selected ones of the regions A through E can be knit or otherwise constructed or treated to provide more or less compression in a specific corresponding region of the wearer""s body.
To determine the amount of compression provided by a particular stocking, a variety of methods can be utilized. One popular method involves the provision of a three-dimensional substantially leg-shaped device having two bars which extend along the leg portion of the device. At least one of the two bars contains sensors along its length. A stocking is donned on the device in the manner it would be worn on a wearer""s leg, and the bars are spread apart to a specific span designed to correspond to the girth of the human leg which the stocking is adapted to fit. The sensors on the thus-spread bars then register the compression being provided by the stocking along the specific regions thereof. Although this can provide a good reading of the compression provided by the stocking once it is donned, it is a static test and therefore does not give an indication of the other forces created during donning of the stocking by the wearer.
An alternative test involves clamping the stocking and stretching it, then allowing it to recover, while measuring the outgoing tension and forces resisting the return to the original dimension. However, this method does not take into account the effects on the fabric in the vertical direction as a result of the test (e.g., due to the fact that when a knit tubular fabric is stretched at discrete points in the coursewise direction, the tube narrows above and below the point where the fabric is being stretched outwardly.)
In order to obtain an indication of the forces experienced by the wearer""s limb as the stocking is donned, stockings are often tested for the degree of friction which they exhibit when they slide along an object such as a wearer""s limb, with the expectation that the lower the friction, the more easily the article can be donned by the wearer. Such friction tests generally involve placing a piece of the fabric on a flat surface, then putting a carriage on the fabric and measuring the force it takes to slide the carriage across the fabric. While such tests can give an absolute type of value for the surface friction, they are less appropriate for testing compression-type stockings and in particular, those with graduated degrees of compression. Furthermore, such tests fail to account for the changes the knit fabric undergoes during the donning process. While the fabric is stretched at various positions along its length, such as the longitudinal and transverse deformation and effects thereof on the fabric and article, the stretch resistance and recovery power of the elastic components forming part of the article causes friction between fibers and yarns in the fabric.
With the foregoing in mind, it is an object of the present invention to provide a hosiery testing device including a means to anchor the hosiery in place during the testing and a tester head connected to means for moving the tester head through the hosiery article or moving the hosiery article past the tester head and means for measuring the force used to advance the tester head through the hosiery article. It is a further object of the present invention to provide a method for measuring the donning properties of hosiery.
The apparatus of the present invention includes a support for securing one end of the hosiery in a permanent position, a tester head attached to a rod adapted to be pulled or pushed through the tubular article and means for moving the geometric body of the tension tester head through the tubular article, a load sensor for measuring the tension within the tubular article and a tension measuring and recording device.
It has been found that the donning properties of hosiery may be obtained by securing one end of a tubular article such as hosiery to be tested to a support, inserting a tension testing head within the tubular body, advancing the tester head through the tubular article, and measuring the force used to advance the tester head and the expansion of the tubular article. The tester head has a geometric shape that may be advanced by withdrawing the head through the hosiery or the hosiery may be drawn past the tension head.